/* mbed Microcontroller Library
 * Copyright (c) 2006-2013 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include <stddef.h>
#include "us_ticker_api.h"
#include "cmsis.h"

static ticker_event_handler event_handler;
static ticker_event_t *head = NULL;

void us_ticker_set_handler(ticker_event_handler handler)
{
	us_ticker_init();

	event_handler = handler;
}

void us_ticker_irq_handler(void)
{
	us_ticker_clear_interrupt();

	/* Go through all the pending TimerEvents */
	while (1) {
		if (head == NULL) {
			/*  There are no more TimerEvents left, so disable matches. */
			us_ticker_disable_interrupt();
			return;
		}

		if ((int)(head->timestamp - us_ticker_read()) <= 0) {
			/* This event was in the past: point to the following one and execute its handler */
			ticker_event_t *p = head;
			head = head->next;
			if (event_handler != NULL) {
				event_handler(p->id); // NOTE: the handler can set new events
			}
			/* Note: We continue back to examining the head because calling the */
			/* event handler may have altered the chain of pending events. */
		} else {
			/* This event and the following ones in the list are in the future: set it as next interrupt and return */ 
			us_ticker_set_interrupt(head->timestamp);
			return;
		}
	}
}

void us_ticker_insert_event(ticker_event_t *obj, timestamp_t timestamp, uint32_t id)
{
	/* disable interrupts for the duration of the function */
	__disable_irq();

	/*  initialise our data */
	obj->timestamp = timestamp;
	obj->id = id;

	/* Go through the list until we either reach the end, or find */
	/* an element this should come before (which is possibly the head). */
	ticker_event_t *prev = NULL, *p = head;
	while (p != NULL) {
		/* check if we come before p */
		if ((int)(timestamp - p->timestamp) <= 0) {
			break;
		}
		/* go to the next element */
		prev = p;
		p = p->next;
	}
	/* if prev is NULL we're at the head */
	if (prev == NULL) {
		head = obj;
		us_ticker_set_interrupt(timestamp);
	} else {
		prev->next = obj;
	}
	/* if we're at the end p will be NULL, which is correct */
	obj->next = p;

	__enable_irq();
}

void us_ticker_remove_event(ticker_event_t *obj)
{
	__disable_irq();

	/* remove this object from the list */
	if (head == obj) {
		/*  first in the list, so just drop me */
		head = obj->next;
		if (head == NULL) {
			us_ticker_disable_interrupt();
		} else {
			us_ticker_set_interrupt(head->timestamp);
		}
	} else {
		/* find the object before me, then drop me */
		ticker_event_t* p = head;
		while (p != NULL) {
			if (p->next == obj) {
				p->next = obj->next;
				break;
			}
			p = p->next;
		}
	}

	__enable_irq();
}
